刷新数据库VB.NET

Question

因此，我具有用于数据库的即时消息传递功能。 每次发送消息时，它都会将数据库中消息列中的内容打印到我的vb.net应用程序的富文本框中

我的问题是。 我必须单击两次“发送消息”按钮才能使用该功能，因为我第一次单击该按钮，没有任何反应

有人知道我哪里出错了吗？ 非常感激！

 Try
        '----------------Sends the message-------------------------------------
        MysqlConn.Open() ' opening the connection to the DB
        Dim query As String
        query = "insert into dojodb.chats (Message) values ('" & txtMessage.Text & "')"
        command = New MySqlCommand(query, MysqlConn)
        reader = command.ExecuteReader 'executes the command and reads data from db
        reader.Close()


        '-------------------Retreives the message------------------------------------
        Dim sqlStr As String = "SELECT * FROM chats"
        Dim chatcommand As New MySqlCommand(sqlStr, MysqlConn)
        Dim rdr As MySqlDataReader = chatcommand.ExecuteReader()
        Dim tbl As New DataTable
        tbl.Load(rdr)


        '-------For every row, print the message, skip a line, and add 1 so it goes to next msg--------
        For i As Integer = 0 To tbl.Rows.Count - 1
            rowIndex = i
            strOutPut &= CStr(tbl.Rows(rowIndex)("Message")) & vbNewLine
            i = i + 1
        Next

        txtGroupChat.Text = strOutPut
        strOutPut = "" 'clearing the string so that it does not print out duplicate info next time

        '-------------------------End Retrieve-------------------------------------------

        MysqlConn.Close()
    Catch ex As Exception
        MessageBox.Show(ex.Message) 'printing the exact error to help future testing if needed
    Finally
        MysqlConn.Dispose()
    End Try
End Sub

Answer 1

我认为您的问题是此部分：

'-------For every row, print the message, skip a line, and add 1 so it goes to next msg--------
For i As Integer = 0 To tbl.Rows.Count - 1
    rowIndex = i
    strOutPut &= CStr(tbl.Rows(rowIndex)("Message")) & vbNewLine
    i = i + 1
Next

你为什么跳过一行？ 这将导致表中的所有其他消息都不会被写出，因此这就是为什么您必须按两次以使其显示出来的原因。 您无需在For循环中手动增加索引器，建议您尝试以下操作：

For i As Integer = 0 To tbl.Rows.Count - 1
    rowIndex = i
    strOutPut &= CStr(tbl.Rows(rowIndex)("Message")) & vbNewLine
Next